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Rectal douching by MSM associated with increased odds of infection with HIV and STIs

Rectal douching may put men who have sex with men (MSM) at increased risk of HIV and other sexually transmitted infections (STIs), according to research published in Sexually Transmitted Infections. Synthesising the results of 24 separate studies, investigators showed that rectal douching was associated with increased odds of infection with HIV and STIs including viral hepatitis and bacterial infections such as chlamydia and gonorrhoea.

“This is the first systematic review and meta-analysis known to these authors to quantify associations between rectal douching and HIV/STIs among MSM,” comment the investigators. “High rates of co-occurring risk behaviours, including rectal douching…highlight the need to explore high-risk practices among MSM in a holistic way that accounts for the complex realities of the sexual risk environment.”

The investigators suggest that douching may damage the delicate lining of the rectum, thereby facilitating the transmission of HIV/STIs.

Chlamydia is a common sexually transmitted infection, caused by bacteria called Chlamydia trachomatis. Women can get chlamydia in the cervix, rectum, or throat. Men can get chlamydia in the urethra (inside the penis), rectum, or throat. Chlamydia is treated with antibiotics.

When the statistical data from all studies which relate to a particular research question and conform to a pre-determined selection criteria are pooled and analysed together.

Rectal douching – the insertion of a liquid, such as tap water or soapsuds, into the rectum via a tool, to cleanse the rectum before or after anal sex – is a common activity among MSM. Research suggests that up to half of MSM in the US engage in rectal douching.

Studies exploring the association between rectal douching and HIV/STI risk have yielded conflicting results. A team of researchers at Sun Yat-sen and Shanghai Jiaotong Universities led by Professors Huachun Zou and Yong Cai therefore performed a systematic review and meta-analysis of studies involving MSM that examined the relationship between douching and HIV/STI infections.

They identified a total of 28 studies involving 21,570 MSM. Almost half (46%) were conducted in the US, with over a third (35%) in Europe and the remainder in South America, Asia and Africa. The studies were published between 1982 and 2018.

Half the participants (52%) reported rectal douching. There was a cross-over between douching and high-risk sexual behaviour: 52% of men reporting rectal douching said they had recently had anal sex without a condom and 58% reported a high number of recent sexual partners.

Twenty studies assessed the association between douching and HIV infection, with 17 finding a positive association. Of the 17 studies looking at the relationship between rectal douching and other STIs, three found that douching was associated with increased odds of infection with hepatitis B virus, one for hepatitis C virus, six for chlamydia and gonorrhoea, one for syphilis and two for multiple bacterial and viral STIs, while five found no association with the STIs examined.

A total of 24 studies (20,398 participants) had sufficient statistical analyses to be included in the meta-analyses.

The odds of HIV infection among men who practiced rectal douching were increased almost threefold (OR = 2.8; 95% CI, 2.32-3.39), an association that remained robust after adjustment for potential confounders (OR = 2.74; 95% CI, 2.14-3.50).

The pooled results of the 15 studies that looked at the association between rectal douching and other STIs found that the practice was associated with a more than twofold increase in the risk of an STI other than HIV (OR = 2.46; 95% CI, 1.95-3.11). Specifically, rectal douching was associated with a threefold increase in the odds of infection with hepatitis B or C, and also of chlamydia and gonorrhoea.

After taking into account potential confounders, rectal douching remained associated with a more than twofold increase in the odds of an STI (OR = 2.27; 95% CI, 1.70-3.04).

But was the relationship between rectal douching and an increased risk of HIV and other STIs simply because MSM engaging in douching were more likely to have anal sex without a condom? The authors don’t dismiss this possibility but think it unlikely, noting that most of the studies performed multiple analyses to take into account potential confounders such as sexual risk behaviour and partner numbers. Findings were robust in an analysis that only included these studies.

The investigators believe there are several reasons why the association between rectal douching and increased HIV/STI risk is biologically plausible:

Damage to the delicate lining of the rectum.

Removal of protective naturally occurring bacteria.

Transmission of infections through sharing of douching tools.

The researchers acknowledge that their research is subject to several limitations, especially the observational design of all the studies included in the meta-analyses. They note that the studies do not record enough information about potential contributory factors, such as whether douching occurs before or after sex, the types of liquids used, and the types of tools used.

“More studies are needed to examine co-occurring high-risk sexual behaviours among MSM who practice rectal douching,” conclude the authors. “Our results suggest the need for health education materials that inform MSM about the potential increased risk of HIV/STIs if they choose to douche before or after anal sex.”

Li P et al. Association between rectal douching and HIV and other sexually transmitted infections among men who have sex with men: a systematic review and meta-analysis. Sex Transm Infect, doi.10.11/sextrans-2019-053964.

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